Public Displays of Affection May Have Evolutionary Benefits

Tia Ghose, LiveScience Staff Writer

Date: February19 2013

Monogamous animals such as the Great Crested grebe may continue with public displays like the weed dance after pairing up because it increases their offsprings' chances of survival CREDIT: © Emiko Paul, reproduced with permission from: Price, T. 2008 View full size image

Those goodbye hugs at the train station or quick kisses in the park may have deep evolutionary roots. Such public displays of affection may help pair-bonded couples invest more in their children, boosting the offspring's survival odds, new research suggests.

The study, published today (Feb. 19) in the journal Proceedings of the Royal Society B, finds that when monogamous animals such as birds continue their displays after mating, they put more energy into parenting and can have more children than when they drop the displays.

 



Lifelong mates
 

Birds and other animals use showy feathers or elaborate courtship behaviors such as mating dances to lure potential partners.

But in the early 1900s, biologist Julian Huxley noticed that birds known as Great Crested grebes rise up out of the water like synchronized swimmers with weeds in their beaks. They continued this elaborate mating ritual, which Huxley likened to humans holding hands or kissing, even after mating.
That begged the question: Why would monogamous animals have evolved to continue these display once they'd paired up?

"It's very obvious why you'd want a display to attract a mate, but once you've already secured a mate, why should you bother to keep displaying?" said study author Maria Servedio, an evolutionary biologist at the University of North Carolina, Chapel Hill.

After all, bright colors and public displays of affection are energetically costly and make animals more visible to predators. The evolutionary benefits have to outweigh the costs for animals or they wouldn't bother.

Helping the kids

To find out, Servedio and her colleagues looked at existing studies from the animal kingdom. They noted that in monogamous species, paired-up animals are better at raising more offspring. In other words, two individual birds may be able to raise one chick at a time, but a couple can raise more than two chicks together.

The researchers also found that, in other studies, when researchers covered up mating displays like a bright red spot on a bird's bill, the animals' partners invested less in offspring, Servedio told LiveScience. Emphasizing an animal's display also seemed to increase its investment in offspring.
Researchers then used a mathematical model to see if those two effects could make displays that continue through a pair-bonded relationship evolutionarily beneficial. The scientists found that this was in fact true, because the displays made couples more likely to invest in their offspring, increasing their reproductive fitness.

Human effect?

The findings suggest that monogamous animals like humans snuggle, sport flashy feathers or canoodle on the subway because it increases parents' investment in young, and thus, increases the odds of these children surviving.

"This study points out a fascinating potential for these mutual displays to be adaptive in terms of gains in parental investment by both sexes," Rebecca Safran, an evolutionary biologist at the University of Colorado, Boulder, who was not involved in the study, wrote in an email.

While its implications are most obvious for birds, "it is not such a long stretch to imagine this process at work in human populations. The trick is that the signals used by humans to stimulate additional parental care would likely differ by culture and social context," Safran said.

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Skull of world's oldest penguin found

'Wrapped it in newspaper, left it in my garage'

SAM SACHDEVA

Last updated 14:31 19/02/2013

JOHN KIRK-ANDERSON/Fairfax NZ
Amateur fossil hunter Al Mannering, who discovered the skull of the world's oldest penguin, left, which is shown compared with a modern penguin.

The skull of a 65-million-year-old penguin which spent the last decade wrapped in newspaper in a Christchurch garage could unlock the secrets of the bird's evolution. Canterbury Museum scientists are analysing the new fossil of Waimanu manneringi, named after the Christchurch amateur fossil hunter who was the first to find bones from the world's oldest penguin.

Al Mannering, who first found fossils of the bird at the Waipara River in 1997, made the new find in 2003 but did not realise its significance until preparing it late last year. 'I wrapped it in newspaper and left it in my garage for 10 years, then last year I thought, 'I'd better have a go at that. Once I realised what it was, I emailed [the museum] straight away.''

Canterbury Museum senior curator Paul Scofield said the fossil, from the Paleocene era, was in ''exceptional'' condition. ''On a worldwide basis, it would be as good as fossils of this age get.'' Scofield said the skull was one of the most important parts of the body for paleontologists, providing valuable hints about the bird's history and its connection to other penguins.

Museum scientists would compare the skull with those of thousands of other penguins to develop a ''family tree'' and determine how the bird related to both modern penguins and the dinosaurs. The researchers would also do a CT scan of the skull at Christchurch Hospital, allowing them to reconstruct its brain and outline its abilities and lifestyle. ''As birds become specialists in flight or diving, it changes the way their brain works: now we can start to make guesses at how these animals actually lived,'' Scofield said.

The museum would work with American scientists from the University of Texas who had found similar fossils in South America, which had recently separated from New Zealand at the age the fossils dated back to. ''It's a really sexy field in paleontology, because penguins were one of the earliest bird groups to evolve.''

Scofield said the Paleocene era was ''absolutely crucial'' to scientific understanding of modern birds and mammals, due to dramatic change which occurred during the period. ''As soon as we became free of dinosaurs, evolution went crazy,'' he said.

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Tristan da Cunha and the Rockhopper Penguin

Image acquired February 6, 2013 download large image (323 KB, JPEG, 1440x960) 

 

 

The island of Tristan da Cunha is located in the southern Atlantic Ocean—more than 3,700 kilometers (2,300 miles) from the coastline of Antarctica, approximately 2,800 kilometers (1,700 miles) to the southern tip of Africa, and more than 3,000 kilometers (1,900 miles) from the east coast of South America. The island forms part of the British Overseas Territory of Saint Helena, Ascension, and Tristan da Cunha. The shoreline of the 13 kilometer (8 mile) wide island is marked on most sides by steep cliffs, with lower beach areas on the southern and north-northwestern sides. The island is notable for its bird population and includes important breeding grounds for petrels, albatrosses, penguins, and shearwaters.

Tristan da Cunha is a shield volcano, a volcanic structure with a low, broad profile and composed of silica-poor lavas (such as basalt). The upper surface of this low base appears dark green in this astronaut photograph. Steeper brown to tan colored slopes mark the central cone of the volcano at the island’s center. The summit crater, Queen Mary’s Peak, sits at an elevation of 2,060 meters (6,760 feet) above sea level. While geologic evidence indicates that eruptions have occurred from the central crater, lavas have also erupted from flank vents along the sides of the volcano and from smaller cinder cones.

The last known eruption of Tristan da Cunha took place in 1961–1962 and forced the evacuation of the only settlement on the island, Edinburgh of the Seven Seas, on the northern coastline (obscured by clouds in this image). The town is considered to be the most remote permanent settlement on Earth, with its nearest neighbor located 2,173 kilometers (1,347 miles) to the northeast on the island of St. Helena.

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Northern Rockhopper Penguin

(Eudyptes Moseleyi)

Written by: Lisa Triggs, Biology 487, Winter 2009 Eudyptes moseleyi StatusEndangered (IUCN) The current listing of endangered is appropriate at this time.  Current protection consists of marine protected areas/reserves, montoring of populations, and ecological and demographic studies. Conservation Concerns   Past human explotation and introduced predators. Food supplies may be affected by fisheries, climate change and shifts in marine food webs. Increasing disturbance and pollution results from exotourism and fishing. Eggs taken for food and birds taken for oil. Introduced predators may affect breeding success. Global changes are causing a decrease in primary productivity and an increase in sea surface temperatures. There has been a rapid population decrease over the last 30 years throughout this penguin's range. Precise reasons for the declines are poorly known but changes in sea surface temperature, competition and incidental capture in fisheries and introduced predators are likely to be implicated. Possible Actions  Continue to monitor or start to monitor populations to assess trends. Conduct studies to assist in interpreting population changes. Conduct studies to assess the impacts of interactions with commercial fisheries. Investigate the impact of introduced species at breeding colonies and eradicate introduced species where necessary. Investigate the impact of oil exploration and exploitation. Study the impacts of climate change. Reduce disturbance from ecotourism. Create more marine protected areas. Reduce/exclude large scale commercial fishing from within prescribed distances from penguin breeding locations. Distribution Descriptive Characteristics  Adult males and females are similar.  They have a thin, yellow supercillium with longer plumes and red eyes. Juveniles have a faint yellow stripe above their eyes and the red brown bill of adults.  They have a pale, mottled gray chin. The chicks lack the yellow crest and the red-brown bill of adults. Their bills are black.  They have grey-black backs and white fronts. There is a very small degree of sexual dimorphism between the sexes. The females are slightly smaller with an average female to male bill depth ratio of .85. Calls are noisy, aggressive and demonstrative; raucous, braying sounds; more strident, pulsed squeaks, separated by shorter periods of silence; shrill and unmusical. Four types of calls exist - contact, sexual, agonistic and chick. Measurements Males Weight: 3 kg Height: 52 cm Beak Length: 4.83 cm Flipper Length: 17.40 cm Foot Length: 11.70 cm Females Weight: 2.50 kg Height: 52 cm Beak Length: 4.16 cm Flipper Length: 16.90 Foot Length: 10.85 cm Breeding Biology Average Arrival Date: July 30 Average Egg Laying Date: September 15 Incubation Period: 32 days Chick Rearing Period: 66 days Fledging Period: December 01 through December 31 Average Annual Reproductive Success: 1 chick/nest Notes: They lay 2 eggs but usually only one chick survives to fledging. Nest: Nests are located on rocky slopes and amongst tussocks; sometimes in small caves and amongst crevices. A small nest is built from tussock, peat and pebbles. Age at First Breeding: 4 years Maximum Lifespan: 30 years Average Lifespan: 10 years Egg Weight: 76.50 grams Egg Length: 6.21 cm Egg Breadth: 5.03 cm Second Egg Weight: 108.00 grams Second Egg Length: 7.15 cm Second Egg Breadth: 5.33 cm Molt: The molt is very varied depending on the location of the colony and whether there was a fialed breeding or the animal was a non-breeder.  The length of the molt is approximately 23-30 days.  The adult molt is pre-nuptial on the breeding sites and follows a pre-molt period at sea of 60 gays. Molt normally is in March. Predators Eggs and chicks are preyed upon by a variety of birds including:  great skuas, brown skuas, striated caracaras, kelp gulls, dolphin gulls and turkey vultures. Adults are preyed upon by fur seals, Southern sea lions, leopard seals, blue sharks and giant petrels Juveniles are preyed upon by fur seals, Southern sea lions, leopard seals, blue sharks and giant petrels. Fledglings are preyed upon by fur seals, Southern sea lions, leopard seals, blue sharks, and giant petrels. Prey  They prefer Crustaceans (euphausids), small fish, and cephalopods (squid). There is a a variability of prey resources at sea for this species and subsequent opportunism of this penguin species to exploit what is differentially available. References source of article

PDF - Rockhopper Penguins (Eudyptes Chrysocome) at Tristan da Cunha

Ecosystem in Penguin Country

Click image for wallpaper size

Figure 1: The marine foodweb of the west Antarctic Peninsula is characterized by large predators such as penguins, seals and whales sustained by upwelling that supports high productivity and large krill populations. Credit I. Heifetz, Rutgers University.

The PAL study region along the western Antarctic Peninsula is one of the most rapidly warming places on the planet (see below), and the ecosystem is responding to the rapid climate warming. Observations of the Antarctic marine food web since the 1970s indicate the development of a more complicated food web with new types of grazers and increased microbial activity (Figure 1). Krill populations - small shrimp-like animals eaten by penguins, seals and whales - are in decline.

Recently, gelatinous salps have been found in nearly every net tow and if krill are replaced by salps it would have important repercussions for the diet of larger predators.

A technique called inverse modeling has helped scientists incorporate their observations into food web models that yield estimates of key ecosystem process like photosynthesis, feeding, respirations and growth rates of krill, salps, penguins and bacteria. Changes they are seeing in the Antarctic presage equally larger changes closer to home.

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Rise of the feathered dinosaurs

An exceptionally well-preserved fossil hints that feathers might have been a feature of all dinosaurs.

• Brian Switek

02 July 2012

 

The fossil of an ancient theropod found in Germany indicates that feathers were widespread in dinosaurs.

Helmut Tischlinger

Feathers didn’t start with birds. Plumage of various sorts — from simple fuzz to the complex structures used for flight — adorned dinosaurs first, and was only later inherited by birds. And if a beautifully preserved juvenile dinosaur unearthed in the Jurassic strata of Germany is any indication, it is possible that all dinosaurs bore patches of filamentous feathers.

Since the discovery of the fluffy theropod Sinosauropteryx in 1996, palaeontologists have recognized more than 30 types of feathered dinosaur. Most of these are coelurosaurs — a disparate group of theropods that includes not only the fearsome tyrannosaurs, sickle-clawed deinonychosaurs and bizarre therizinosaurs, but also birds.

However, there are exceptions to this rule. Palaeontologists have also discovered simple, feather-like structures along the vertebral columns of the dinosaurs Psittacosaurus and Tianyulong. These ornithischians are about as distantly related to birds as dinosaurs can be, and the discoveries hinted that swaths of simplified protofeathers were a common feature among dinosaurs. The discovery of the most recent fossil indicates that feathery body coverings were widespread in these creatures.

Ancient adornment

The 150-million-year-old theropod Sciurumimus albersdoerferi unearthed in Germany and described today¹ was coated in a form of plumage. The filamentous structures have been seen before in other dinosaurs, but what makes Sciurumimus so noteworthy is that this dinosaur was a megalosauroid.

Megalosauroids were a group of archaic sharp-toothed dinosaurs near the base of the theropod family tree, and greatly removed from the various types of feathered dinosaur and early birds recognized so far. According to first author Oliver Rauhut, a palaeontologist at the Ludwig Maximilian University in Munich, Germany, this means that simple feathers were a very ancient dinosaur trait. The filaments of Sciurumimus, Rauhut says, are very similar to the simple structures seen in Psittacosaurus, Tianyulong and even pterosaurs — extinct flying reptiles that were the closest cousins that dinosaurs had. The wide evolutionary spread of this characteristic means that protofeathers are probably as old as the Dinosauria itself.

Palaeontologist Paul Barrett of London’s Natural History Museum agrees that the structures on Sciurumimus are probably protofeathers. Although additional geochemical work is needed to study the features' details, Barrett says, the fossilized wisps are very similar to the fuzz seen on other dinosaurs. But he notes that the presence of these filaments among all dinosaurs is “speculation”. Feathery structures might be a common feature of dinosaurs, but it’s also possible that they evolved multiple times. “We need more examples in both non-coelurosaurian theropods, and particularly in the other big dinosaur groups, before we can really speculate that these features are a character of dinosaurs as a whole,” Barrett says.

Rauhut is sure there are many more feathery dinosaurs yet to be found. The trick will be finding specimens in the sorts of fine-grained sediments capable of preserving feather fossil. But on the basis of findings from Sciurumimus and other feathery dinosaurs, Rauhut notes, “all dinosaurs had at least this kind of simple, hair-like feathery integument”. Instead of being a novelty that evolved among particularly bird-like dinosaurs, “feathers seem to be an ancestral dinosaurian trait”, Rauhut says. If so, we will have to start thinking about what kind of feathery covering these creatures display when we depict them in art and film.

Nature

doi:10.1038/nature.2012.10933

References

Rauhut, O. W. M., Foth, C., Tischlinger, H. & Norell, M. A. Proc. Natl Acad. Sci. USA http://www.pnas.org/cgi/doi/10.1073/pnas.1203238109 (2012).

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